Player complaining about lack of first team football during offseason!

So I have a player that's saying he wants to leave for first team football because I'm not playing him - even though the season has finished!

He's a young player with good potential, who did only play a handful of games and was complaining about first team opportunities before. He'd just come back from a lengthy injury though and had a goal and assist in the final game of the season. At this point his morale was very good. Now a matter of days later his morale is abysmal and "the player wants to talk about leaving to get first team football."

Btw I'm in the Russian league which has a short offseason, with no holiday, and a long winter break.

He wasn't used much and sees a move in the offseason as a way of getting 1st team games, reassure him he'll get more chances this season and see what he says, also depending on his potential if he's going to end up an average player, get shot of him.